mirror of
https://github.com/neondatabase/neon.git
synced 2026-01-14 17:02:56 +00:00
adb0526262
## Problem Large quantities of ephemeral layer data can lead to excessive memory consumption (https://github.com/neondatabase/neon/issues/6939). We currently don't have a way to know how much ephemeral layer data is present on a pageserver. Before we can add new behaviors to proactively roll layers in response to too much ephemeral data, we must calculate that total. Related: https://github.com/neondatabase/neon/issues/6916 ## Summary of changes - Create GlobalResources and GlobalResourceUnits types, where timelines carry a GlobalResourceUnits in their TimelineWriterState. - Periodically update the size in GlobalResourceUnits: - During tick() - During layer roll - During put() if the latest value has drifted more than 10MB since our last update - Expose the value of the global ephemeral layer bytes counter as a prometheus metric. - Extend the lifetime of TimelineWriterState: - Instead of dropping it in TimelineWriter::drop, let it remain. - Drop TimelineWriterState in roll_layer: this drops our guard on the global byte count to reflect the fact that we're freezing the layer. - Ensure the validity of the later in the writer state by clearing the state in the same place we freeze layers, and asserting on the write-ability of the layer in `writer()` - Add a 'context' parameter to `get_open_layer_action` so that it can skip the prev_lsn==lsn check when called in tick() -- this is needed because now tick is called with a populated state, where prev_lsn==Some(lsn) is true for an idle timeline. - Extend layer rolling test to use this metric